Immersible oil fence assembly

ABSTRACT

An immersible oil fence assembly including alternately connected oil fence units and immersible buoys. The oil fence units have tubular float means connected to inflatable bags of the immersible buoys. By inflating and deflating the tubular float means and the inflatable bags, the oil fence is selectively floated and immersed. The buoys are anchored to station the oil fence assembly in position.

United States Patent [1 1 Muramatsu et al.

IMMERSIBLE OIL FENCE ASSEMBLY Inventors: Tateo Muramatsu; KuninoriAramaki, both of Yokohama City, Japan Assignee: Bridgestone Tire CompanyLimited,

Tokyo, Japan Filed: Mar. 14, 1972 App]. No.: 234,579

Foreign Application Priority Data Mar. 20, 197! Japan 46/15685 [1.8. CI.61/1 F Int. Cl E02b 15/04 Field of Search 61/1 F, 5; 210/242,

2l0/DlG. 21

[ Dec. 18, 1973 [56] References Cited UNITED STATES PATENTS 3,708,983l/l973 Brown 6l/l F Primary Examiner-Peter M. Caun Attorney-Martin Fleitet al.

[57] ABSTRACT An immersible oil fence assembly including alternatelyconnected oil fence units and immersible buoys. The oil fence units havetubular float means connected to inflatable bags of the immersiblebuoys. By inflating and deflating the tubular float means and theinflatable bags, the oil fence is selectively floated and immersed. Thebuoys are anchored to station the oil fence assembly in position.

12 Claims, 14 Drawing Figures SHEET 02 0F 10 PAIENTEU 05m 8 ms PATENTEI]DEC] 8 I973 SHEEI Oh (if 10 PATENIEUUEBIBIQTS 3,779,020

' sum user 10 Pmmmnmw' 3779 020 sum user 10 PAIENTEU mi 1 81m 1-3. 7751.um

, sum near 10 PAI N use! 8197a SEIEEI 10 0F 10 BACKGROUND OF THEINVENTION 1. Field of the Invention This invention relates to aselectively immersible oil fence assembly, and more particularly to acomparativelysimpleprocess and device for quickly forming a selectivelyimmersible oil fence line at desiredmoment and allowing the oil fenceline to sink so deep in water when it is not in use that ships cannavigate above the oil fence line thus sunk.

2. Description of the Prior Art Duringloading to and unloading from anoil tanker on berth, ata quay or an offshore dolphin, there is a riskthat oil leaked from the piping for the loading or unloading may spreadon the water surface to cause water pollution. To prevent such risk, anoil fence is provided either from the quay side or from the tanker side,so as to enclose the water surface in the proximity of the pipe line forpreventing the oil leakage from spreading beyond the area defined by theoil fence. If such oil fence is a semi-permanent installation providedin the proximity of a quay or a dolphin, it may disturb the navigationof ships and restrict the port function. The semi-permanent oil fencemay also collide with ships and cause damage. The exposure of thesemipermanent oil fence to rugged sea and weather conditions may shortenits service life. On the other hand, if the oil fenceis temporarilyinstalled and removed for each loading or unloading operation, theinstalling and removing work of the temporary oil fence is timeconsuming. Furthermore, temporary oil fences are required to be simplefrom the standpoint of operation and cost, so that it is difficult toensure reliable protection against dispersion of oil leakage.

Therefore, an object of the present invention is to obviate theaforesaid difficulties of conventional oil fence, by providing aselectively immersible oil fence assembly,

SUMMARY OF THE INVENTION According to the present invention, there isprovided an immersible oil fence assembly, in which a tubular floatmeanscarrying an elongated flexible belt member is selectively inflated, soas to selectively form an oil fence line by floating the flexible beltmember on water surface. Upon deflation of the tubularfloat means, theentire oil fence line sinks deep in water, so as to allow shipnavigation above the oil fence line thus sunk. The oil fence assemblyincludes immersible buoys which are anchored through flexible wire ropemeans, so as to re 'peatedly produce the oil fence line substantially ata predetermined protective zone and to prevent the oil fence line fromdrifting beyond the periphery of the protective zone.

With the immersible oil fence assembly of the aforesaidconstruction, thepollution due to oil leakage is effectively prevented, while allowingship navigation above the oil fence which is not in use by immersing theoil fence assembly deep in water. Accordingly, the risk of collision ofthe oil fence with ships and quay is completely eliminated. As long asthe oil fence is sunk in water, it is free from destructive effects ofrugged weather and wave conditions, so that a long service life isensured. With the oil fence assembly according to the prevent invention,an oil fence line can easily be formed on the water surface, simply byinflating the tubular float means. Thus, the complicated andtimeconsuming process of spreading oil fence line, as required inconventional oil fence device carried by tankers or the like iscompletely eliminated.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a schematic plan view of animmersible oil fence assembly according to the present invention;

FIG. 2 is a schematic elevation ofthe oil fence assembly, taken alongthe length of the oil fence line;

FIG. 3 is a perspective view of a buoy, which acts as a connector ofadjacent oil fence units each consisting of a tubular float means and anelongated belt member;

FIG. 4 is a schematic elevation of another immersible oil fenceassembly, according to the present invention;

FIG. 5 is a sectional view of controllable weight member to be used inthe oil fence assembly of FIG. 4;

FIGS. 6A and 6B are diagrammatic illustrations, illustrating dispositionof an oil fence assembly for a quay and an offshore mooring buoy,respectively;

FIG. 7 is a schematic view of an oil fence assembly including animmersible terminal buoy, according to the present invention;

FIG. 8 is a schematic view, similar to FIG. 7, illustrating theimmersible terminal buoy in the sate as immersed in water;

FIG. 9 is an enlarged view of the immersible terminal buoy and relatedconnections;

FIG. 10 is a schematic plan view of an oil fence assembly forming aclosed loop and including two sec tions which are independentlyimmersible, according to the present invention;

FIGS. 11 and 12 are fragmentary perspective views of the oil fenceassembly of FIG. 10, illustrating a joint portion and a weight memberthereof, respectively; and

FIG. 13 is a diagrammatic illustration of another embodiment of thepresent invention. I

Like parts are designated by like numerals throughout the drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENT The invention will now bedescribed in detail by referring to embodiments, as illustrated in theaccompanying drawings.

Referring to FIG. 1, a tanker t is moored to a dolphin d to which asubmarine piping P is connected. An immersible oil fence assemblyaccording to the present invention produces an oil fence line A on watersurface so as to substantially surround the tanker z. The oil fence lineA is formed by a plurality ofoil fence units 1 which are connected byimmersible buoys 2. Each immersible buoy 2 is anchored to sea bed byanchors 3, 3' through wire rope means 4. In the embodiment of FIG. I, apair of ropes 4 are used to connect the immersible buoy 2 to a pair ofanchors 3, 3, but it is possible to station the immersible buoy at apredetermined position by one anchor through one piece of rope. The wirerope means 4 can be replaced with any other suitable flexible connectingmeans, such as a metallic chain. In the preferred embodiment of FIG. 1,the wire rope means 4 for the immersible buoy 2 at each end of the oilfence line A is so disposed as to define an angle of about between thewire rope means 4 and the direction of the oil fence line A. The wirerope means 4 for the buoys at intermediate positions of the oil fenceline A are disposed so as to define a right angle between the wire ropemeans 4 and the direction of the oil fence line A at the buoy 2 to whichthe specific wire rope means is connected. Such angular disposition ofthe wire rope means 4 is preferable from the standpoint of maximizingthe stability of the oil fence line A against wind and tide load to theoil fence units 1.

Each oil fence unit 1 consists of an elongated flexible belt member 6,e.g., an elongated rubber belt, and a flexible tubular float means 7extending along the longitudinal center line of the belt member 6. Boththe belt member 6 and the tubular float member should be flexible enoughto allow the float unit 1 to flex along the profile of water surface. Inthe illustrated embodiment of the invention, as shown in FIGS. 1 to 3,the tubular float means 7 consists of a pair of flexible tubular floats7 and 7 secured to the opposite surfaces of the flexible belt member 6.To ensure that the width direction of the elongated belt member 6 isheld substantially vertically across the water surface, oppositelongitudinal ends of the belt member 6 are secured to the immersiblebuoys 2 in vertical posture, as shown in FIG. 3. Suitable weight members5 may be embedded in that longitudinal edge of the belt member 6 whichis to be held in water.

Referring to FIG. 2, a permanently floating pilot buoy 9 is disposed inthe proximity of that immersible buoy 2 which is connected to one end ofthe oil fence assembly, and the pilot buoy 9 is connected to the anchor3 of the end buoy 2 through a separate wire rope means 10. This wirerope means can be a metallic chain, too. In the embodiment of FIG. 2,the wire rope means 10 for the pilot buoy 9 is connected to the wirerope means 4 of the end buoy 2 of the oil fence assembly. The pilot buoy9 carries an air valve-coupling ll communicating with the end buoy 2 ofthe oil fence assembly through a flexible air pipe 8. This coupling 11includes an air valve and controls the air flow into and out of theimmersible oil fence assembly, so that the coupling 11 must always bekept above water surface or must be watertightly closed by a suitablelid so as to selectively be opened for the air flow control.

Let it be assumed that the immserible buoys 2 and the tubular floatmeans 7 of the oil fence assembly are deflated and the entire assemblyrests on sea bed, as shown by phantom lines in FIG. 2. A lighter 12carrying an air source, e.g., an air pump or a compressed air tank,berthes the pilot buoy 9 to connect the air source to the airvalve-coupling 11 for feeding air into the immersible buoys 2 and thetubular float means 7 of the oil fence assembly, through the flexibleair pipe 8. Thereby, the buoys 2 and the float means 7 are inflated, andwhen the buoyancy acting on them reaches a certain predetermined level,i.e., in excess of the total mass of the oil fence assembly, the entireoil fence assembly moves up to the water surface, so as to define theaforesaid oil fence line A. In this case, the air to be delivered to theoil fence assembly through the air valve-coupling 11 should preferablybe pressurized to the extent necessary for overcoming the hydraulicpressure acting on the tubular float means 7 and the immersible buoys 2.i

In the embodiment, as illustrated in FIGS. 1 to 3, it should be notedthat the air valve-coupling 11 is provided only at one end of the oilfence assembly. With such arrangement, upon inflation of the tubularfloat means 7 and the immersible buoys 2, the oil fence assembly maysmoothly move to the water surface from the coupling side end thereof,while upon deflation of the float means 7 and the buoys 2, the oil fenceassembly smoothly sinks starting from the end opposite to the airvalve-coupling l 1. If two or more couplings and two or more valves areprovided, air may inadvertently be entrapped at intermediate portions ofthe tubular float means, so that it becomes difficult to effect smoothsinking of the oil fence assembly.

Instead of being secured to the pilot buoy 9, the air valve-coupling 1 1for the flexible air pipe 8 may be provide at the dolphin d or a portquay.

If the flexible air pipe 8 is strong enough, the pipe8 itself may serveas a wire rope for connecting the pilot buoy 9 to the anchor 3, so thatthe separate wire rope means 10 for the pilot buoy may be dispensedwith. On the other hand, if the flexible air pipe 8 is not so strong asto hold the pilot buoy 9 by itself, the flexible air pipe 8 shouldpreferably be twined about the wire rope means 4 and 10 to supplementits strength.

Each of the immersible buoys 2 includes an inflatable air bag 14, asshown in FIG. 3. The tubular float means 7 of the adjacent float-units 1are connected through the air bag of the immersible buoy 2 locatedtherebetween. The flexible air pipe 8 extending from the airvalve-coupling 11 carried by the pilot buoy 9 is terminated at the airbag 14 of the end buoy 2 of the oil fence assembly, which air bag 14acts as the terminal of the tubular float means 7 of the oil fenceassembly. If two flexible tubes are used to form the tubular float means7, as shown in FIG. 2, the immersible buoys 2 located at intermediateportions of the oil fence assembly may have a unitary air bagcommunicating with the two tubular floats in common or a pair ofseparate air bags 14 connected to the two tubular floats at oppositesides of the belt member 6, respectively.

FIG. 3 illustrates an immersible buoy having a unitary air bag. The buoy2 has a perforated casing 13 housing an inflatable air bag 14 made offlexible material, such as rubber. Two tubular fixtures 15 are securedto one side wall of the perforated casing 13 so as to communicate withthe inside of the air bag 14, while two other tubular fixtures 16 aresecured to the opposite side wall of the perforated casing 13 so as tocommunicate with the inside of the air bag 14. The two tubular fixtures15 or 16 may be connected to the two tubular floats 7 and 7' of thecorresponding float units 1, respectively. If the tubular float means 7of each float unit 1 consists of only one tubular float 7, theimmersible buoy 2 may have two tubular fixtures, one on each of theopposite walls thereof. In the case of the immersible buoy 2 at eitherone of the longitudinal ends of the belt member 6, those tubularfixtures which are not used for the float units 1 or the flexible airpipe 8 are airtightly plugged.

An eye-ring 17 is integrally formed with the bottom wall of theperforated casing 13 of the immersible buoy 2, as shown in FIG. 3. Oneor two wire rope means 4 are swingably connected to the eye-ring 17 forconnecting the immersible float 2 to the anchor 3 or anchors 3, 3'associated thereto.

As described in the foregoing, with the immersible oil fence assemblyaccording to the present invention, the oil fence line can easily besunk under water simply be deflating the tubular float means and thebuoys, so as to provide for free navigation of ships above the oil fenceassembly thus sunk. When protection of water surface by the oil fenceassembly is necessary, it can easily be brought up to the water surfacesimply by inflating the tubular float means and the immersible buoys.

FIG. 4 shows a modification of the oil fence assembly of FIGS. 1 to 3,in which a controllable weight member is added for ensuring smoothsinking and floating operation. In FIG. 4, a plurality of oil fenceunits 1 are interconnected by immersible buoys 2 which are connected toanchors 3 through wire ripe means 4. The construction of the immersiblebuoy 2 and the oil fence unit I is substantially identical with that asdescribed in the foregoing by referring to FIGS. 1 to 3. To inflate anddeflate air bags of the buoys 2 and flexible tubular float means 7 ofthe oil fence units 1, air is forced into or removed from the oil fenceassembly through a flexible air pipe 18, in the same manner as thepreceding embodiment. A controllable weight member 18 secured to anintermediate point of the wire rope means 4 connecting the far end buoy2, as seen from the flexible air pipe 8, to the associated anchor 3. Inthe embodiment of FIG. 4, the controllable weight member 18 consists ofan immersible buoy which is substantially identical with the buoy 2between the adjacent oil fence units 1, except that the controllableweight member 18 does not have any tubular fixture but has a top airpassage formed at the top portion of outer housing of the buoy so as tocommunicate with the inside of an air bag thereof. The immersible endbuoy 2, to which the controllable weight member 18 is connected throughthe wire rope means 4, also has a top air passage 20 similar to that ofthe controllable weightmember IS. The top air passage 20 of the end buoy2 is connected to the top air passage 20 of the controllable weightmember 18 through a flexible end air hose 19, as shown in FIG. 4.

When the oil fence assembly of this embodiment is afloat on watersurface, the controllable weight member 18 is held between the watersurface and the ground level below the water, at a position lower thanany of the immersible buoys 2 and the oil fence units 1. When it isdesired to cause the oil fence assembly of FIG. 4 to sink, the air inthe air bags of the immersible buoys 2 and the tubular flexible floatmeans 7 is released through the flexible air pipe 8 by opening asuitable control valve (not shown). It should be noted here that, sincethe controllable weight member 18 is held at the lowest level of theentire oil fence assembly, the air in the weight member 18 is releasedat first. Accordingly, the buoyancy acting on the controllable weightmember 18 is reduced at first, so that the far end of the oil fenceassembly, as seen from the flexible air pipe 8 begins to sink at first,so as to cause an upward slope in the tubular float means 7 from its farend toward the flexible air pipe 8. Such upward slope ensures smoothsinking ofthe entire oil fence assembly, because it eliminates the riskof entrapping air at any intermediate portion of the tubular float means7 and the immersible buoys 2.

On the other hand, when it is desired to raise the oil fence assembly ofFIG. 4 from ground level to the water surface, airis forced into thetubular float means 7 of the oil fence units 1 and the air bags of theimmersible buoys 2, through the flexible air pipe 8 by actuating asuitable air source (not shown). It is easier to increase the buoyancyof the oil fence assembly in the proximity of the flexible air pipe 8that in its far end. because an extra weight member 18 is connected tothe far end of the oil fence assembly. Thus, the oil fence assemblybegins to float, starting from the side where the flexible air pipe isconnected. As a result, :a downward slope is caused from the proximityof the joint to the flexible air pipe 8 toward the far end of the oilfence assembly. This downward slope ensures smooth raising of the oilfence assembly from the ground level to the water sur face. The positionof the anchor 3 associated with the far end buoy 2 and the total lengthof the wire rope means 4 between the end buoy 2 and its associatedanchor 3 are so chosen that the controllable weight member 18 nevercomes above the lowest part of the air bags of the buoys 2 and thetubular float means 7. Consequently, the aforesaid smooth sinkingoperation is ensured.

As a result of numerous tests, the inventors found that a preferredembodiment of the controllable weight member 18 had an empty weight in.air of about 250 Kg, an air filled weight in sea water of about 30 Kg,and a sea water filled weight in sea water of about 200 Kg. With theembodiment of the aforesaid weight, the preferable depth H of thecontrollable weight member 18 from the water surface when the oil fenceassembly is afloat, as shown in FIG. 4, was found to be about 3 metersto about 5 meters.

FIG. 5 illustrates a bottle-like weight member 18a which can be used asthe controllable weight member 18 in the oil fence assembly of FIG. 4.The bottle-like weight member has a flat top wall with an air passage 20extending through the top wall. The bottom wall of the bottle-likeweight member 18 is contracted, so as to form a water passage 21 at thecentral portion thereof. With simple construction of the bottle-likeweight member 18a, as shown in FIG. 5, all the functionsof thecontrollable weight member 18 of FIG. 4 can be accomplished, as caneasily be understood by those skilled in the art. For safety, it ispreferable to provide a check valve between the air passage of thebottle-like weight member 18a and the end buoy 2 of FIG. 4, in serieswith the flexible end hose 19, lest water should enter into the air bagsof the immersible buoys 2 and the tubular float means 7.

The use of a controllable weight member has been described by referringto an embodiment related to a linear oil fence assembly, but it is alsoapplicable to an oil fence assembly defining a closed loop. In the caseof a loop-defining oil fence assembly, a controllable weight member 18and a flexible air pipe 8 for feeding and releasing air are preferablylocated at diametrically opposite parts of the loop definedby anelongated belt member 6 of the oil fence assembly.

FIGS. 6A to 9 illustrate a means for establishing closing contactbetween one longitudinal end portion of an immersible oil fence assemblyand a ship or a quay. Referring to FIG. 6A, a tanker T is berthed to adolphin d, and it is sometimes desirable to have a closing contact 27between the end portion of oil fence line A I and the tanker T.Similarly, for certain applications, a closing contact 27 is desirablebetween oil fence line A and the surface of a quay O, as shown in FIG.68. It is known that the sea level may vary 2 to 5 meters due to tidealone, and the water line of a large 200,000-ton tanker may vary by 12to 13 meters by loading and unloading. Accordingly, simple connection ofthe end portion of an oil fence assembly to the tanker T or quay Q,e.g., by a rope, is not sufficient to ensure the aforesaid closedcontact for all water levels and water lines. More particularly, if anend buoy 2 of immersible oil fence assembly is connected to a bitt 22 oftanker T (see FIG. 7) by a rope so as to establish a closed contactbetween the end portion of the oil fence assembly and the tanker Twhenthe tanker is unloaded, then upon loading of the tanker, the waterline of the tanker may be lowered by, for instance 12 meters, and theend portion of the oil fence assembly may be drifted away from thetanker T in response to such lowering of the water line, despite theaforesaid rope connection.

Referring to FIGS. 7 and 8, an eye-ring 23 is integrally formed with anend buoy 2 of oil fence assembly, through which a rope 26 is extended.One end of the rope 26 is fastened to the bitt 22 of a tanker T whilethe opposite end of the rope 26 is connected to an immersible terminalbuoy 24. The construction of the terminal buoy 24 is, for instance,similar to the immersible buoy 2, as shown in FIG. 3, except that thebuoy 24 is connected only to a felxible hose 25 but not to float means7. The flexible hose selectively communicates the terminal buoy 24 tothe end buoy 2 of the oil fence assembly through a control valve 34, asshown in FIG. 9.

To connect the terminal buoy 24 to the bitt 22 of the tanker T, or thequay Q, an air bag of the terminal buoy is communicated with the airsystem of the oil fence assembly through the control valve 34, so thatthe terminal buoy 24 floats, and the rope 26 from the bitt 22 passesthrough the eye-ring 23 of the end buoy 2 of the oil fence assembly andit is then fastened to the terminal buoy 24. After the rope 26 is thusconnected, the air in the terminal buoy 24 is released by turning arotor R of the control valve 34 to a position as shown in FIG. 9.Thereby, the terminal buoy 24 sinks by loosing its buoyancy, as shown inFIG. 8. The weight of the terminal buoy 24 acts to pull the end buoy tothe tanker T or the quay Q, so that a closing contact 27 is establishedby an end belt member 6a of the oil fence assembly and the tanker T (orquay Q), as shown in FIG. 9.

As apparent from FIG. 8, the terminal buoy 24 moves in water response tothe tidal water level variation and the water line variation of thetanker T. Thus, a tight contact 27 is ensured between the end portion ofthe oil fence assembly and the tanker T or quay Q.

To disconnect the oil fence assembly, the air bag in the terminal buoy24 is inflated by suitable turning the rotor R of the control valve 34for the feeding air from the oil fence assembly to the terminal buoy 24through the air hose 25. Whereby, the terminal buoy 24 floats on thewater surface. Accordingly, the rope 26 can be released from the buoy24, and such releasing operation can be done on water surface.

A preferred example of the terminal buoy 24 weighs 300 Kg in air, and itproduces a buoyancy of 400 Kg in water upon evacuation thereof.

FIGS. to 12 illustrate an immersible oil fence assembly having twosections, each section being immersible independently of the othersection. Referring to FIG. 10, two tankers T1 and T2 are berthed to amooring station M having a mooring post 29, and a closed oil fence lineA is formed around the two tankers. In order to allow one of the twotankers T] and T2 to leave the mooring station M, it is highly desirableto immerse only one half of the oil fence line A.

The oil fence line A is formed by using the aforesaid oil fence units 1each having an elongated belt member 6 and tubular float means 7, whichunits 1 are interconnected by immersible buoys 2 connected to anchors 3through wire rope means 4. The oil fence line A is looped by connectingopposite ends la and lb together while disposing the central portion 10of the line A at a diametrically opposite position of the loop, as shownin FIG. 10.

FIG. 11 shows the connection of the opposite ends la and lb of the oilfence line A. A suitable connecting strap 6a is rivetted to the beltmembers 6 of the two ends la and lb, for completing the closed loop ofthe elongated belt member 6 for the oil fence line A. The tubular floatmeans 7 at the ends la and lb of the oil fence assembly is blocked byend tubes 7a and 7b. A suitable air source S, e.g., an air pump, isconnected to a flexible air pipe 8 through a main air valve 30, and theend tubes 7a and 7b are connected to the flexible air pipe 8 throughbranch pipes-8a and 8b, respectively. The air flow through the branchpipes 8a and 8b are controlled by branch air valves 31a and 31b mountedon the branch pipes, respectively. When all the branch air valves 31aand 31b are open to allow free air passage therethrough, the floatingand immersion of the oil fence line A can be controlled in the samemanner as described in the foregoing by referring to FIGS. 1 to 3.

In making the looped oil fence line A, it is desirable to provide atension member 28, e.g., a nylon rope, along the tubular float means 7,as shown in FIG. 11. The embodiment of FIG. 11 also includesreinforcements 5a embedded in the belt member 6, together with weightmembers 5.

FIG. 12 shows a weight member 32 connected to the central portion 1c ofthe oil fence line A. The weight member 32 is mechanically connected tothe tubular float means 7 of the oil fence assembly through verticallydisposed flexible air pipe means 33. The mass of the weight member 32 isselected to be balanced with or slightly greater than the buoyancyproduced by the vertically disposed air pipe means 33.

In operation, upon floating the entire oil fence line A, all the branchair valves 31a and 31b are blocked. When the branch air valves 31a andthe main air valve 30 are opened for partially releasing air from theoil fence assembly, the weight member 32 at the central portion 10begins to sink, and that half of the oil fence line which extends to theend la begins to sink. The reason for it is as follows. The verticallydisposed flexible air pipe means 33 is exposed to hydraulic pressure inwater, so that upon release of the air the pipe means 33 is at firstcontracted by the hydraulic pressure. Accordingly, the mass of theweight member 32 surpasses the buoyancy acting on the pipe means 33, sothat the weight member 32 sinks at first. Thereafter, those portions ofthe tubular float means 7 lying between the weight member 32 and thebranch valves 31a is contracted by the hydraulic pressure, because airis released therefrom. Such contraction gradually propagates from thecentral portion 10 to the end portion 1a, because the weight member 32at the central portion 1c sinks at first. At the moment, the otherportion of the oil fence line A, i.e., from the central portion 1c tothe end portion lb, stays afloat, although the close proximity of thecentral portion 10 may partially sinks. More particularly, once theweight member 32 causes central portion 10 to sink, the tubular floatmeans 7 between the central portion lc and the end portion lb isisolated from the opposite half of the oil fence line A, because thetubular float means is contracted by the hydraulic pressure at thecentral portion 1c and air passage is blocked there. Thus, even if alimited suction is applied to the end portion la, that half of the oilfence line A which lies between the central portion 1c and the endportion lb stays afloat.

It is apparent that similar selective immersion can be applied to theopposite half of the oil fence line A, simply by opening the branch airvalves 31b and the main air valve 30, while keeping the branch airvalves 31a as blocked.

After either half of the oil fence line A is thus sunk, one of thetankers T1 and T2 can move above the oil fence portion thus sunk.

It should be noted that such partial immersion of the oil fence line canbe accomplished even if the oil fence line A is not looped but opened,as long as air valves are provided at the opposite ends of the oil fenceline.

FIG. 13 shows another embodiment of the present invention. In thisembodiment, the immersible buoys 2 of FIGS. 1 to 3 are replaced with abuoyancy generating means each has a construction similar to the oilfence unit 1. More particularly, each of the buoyancy generating meansof FIG. 13 comprises a flexible belt member 2d similar to the beltmember 6 of the unit 1 and one or two inflatable tubes 2a secured to thebelt member 2d at one or two opposing surfaces thereof by strap members2!). The strap member 2b may be rivetted to the belt member 2d. Thediameter of the inflatable tube 2a is considerably greater than that ofthe tubular float means 7, because the former is required to generate abuoyancy large enough for floating both the buoyancy generating meansitself and a wire rope means 4 anchoring the buoyancy generating meansto sea bed. In the embodiment of FIG. 13, the wire rope means 4 isconnected to the buoyancy generating means at an eye-ring 20 provided atthe aforesaid strap 2!). The opposite end of the wire rope means isconnected to a heavy concrete block 3a sitting on the sea bed. The wirerope means 4 of the embodiment includes chains at a part thereof.

The embodiment of FIG. 13 further includes a solid weight member 32connected to that buoyancy generating means which is located at thenon-ar-supply end of the oil fence line A. The weight member 32 is hangfrom the oil fence line A by an inflatable tube 33 communicating withthe inflatable tube 20 of said buoyancy generating means located at saidend of the oil fence line A. The construction and operation of theweight member 32 and the inflatable tube 33 of FIG. 13 are essentiallyidentical with those of similarly numbered weight member and inflatabletube in the embodiment of FIGS. I1 and 12. Accordingly, the solid weightmember 32 ensures smooth sinking and floating of the oil fence assembly.

Salient features of the present invention can be summarized as follows.

l. A highly effective oil fence assembly having an elongated beltmember, which belt member can extends above water level by aconsiderably large extent for ensuring effective blocking of floatingdrifts, can selectively be immersed by simple air valve operation, forallowing ship navigation above the oil fence assembly thus sunk. l

2. The formation andremoval of the oil fence line can be carried outvery quickly.

3. With the use of a looped oil fence line or an immersible terminalbuoy, complete blocking of oil or other floating drifts is ensured.

4. The drifting of the oil fence line itself due to wind or tide can beprevented by anchoring the immersible buoys of the oil fence assembly.

5. Partial immersion of the oil fence line is possible.

What is claimed is: I

1. An immersible oil fence assembly, comprising a plurality of oil fenceunits having an elongated flexible belt member and a tubular float meanssecured to the belt member so as to extend along the longitudinal centerline of the belt member, a plurality of immersible buoyancy generatingmeans having an inflatable air container disposed therein, said oilfence units and said buoyancy generating means being alternatelyconnected while joining said tubular float means of adjacent ones ofsaid oil fence units to said air container of the buoyancy generatingmeans located therebetween, so as to form an oil fence line, anchorsstationed on the ground level, wire rope means connecting each of saidanchors to corresponding one of said immersible buoyancy generatingmeans, respectively, said wire rope means being long enough to cause thebuoyancy generating means to float on water surface, a blocking meansairtightly blocking said tubular float means at one end of said oilfence line, a flexible air hose connected to the opposite end of saidoil fence line, and an air valve means connected to said air hose andselectively feed ing and releasing air into and out of said tubularfloat means and said air container of the buoyancy generating means.

2. An immersible oil fence assembly according to claim 1, wherein eachsaid buoyancy generating means is an immersible buoy having aninflatable air bag surrounded by a perforated shell.

3. An immersible oil fence assembly according to claim 1, wherein eachsaid buoyancy generating means is a second oil fence unit consisting ofa second belt member aligned with said belt member of said oil fenceunit, an inflatable second tubular float means aligned with the tubularfloat means of said oil fence unit and having a diameter larger thanthat of saidtubular float means of the oil fence unit, and a metallicstrap means integrally bonding said second tubular float means to saidsecond belt member.

4. An immersible oil fence assembly according to claim 1 and furthercomprising a pilot float means anchored to ground level through a wirerope means so as to float on water surface substantially at a constantlocation, said air valve means being mounted on said pilot buoy.

5. An immersible oil fence assembly according to claim 1 and furthercomprising a controllable weight member secured to the wire rope meansconnecting the blocked side end buoyancy generating means to the anchorassociated with said end buoyancy generating means at anintermediateposition between said end buoy and said associated anchor,said controllable weight member having an inflatable air chamber, and aflexible air hose connecting air container of said end buoyancygenerating meansto said air chamber of said controllable weight member,the connecting position of said controllable weight member to said wirerope means being such that said controllable weight member is alwayskept below water level.

6. An immersible oil fence assembly according to claim 5, wherein saidcontrollable weight member is an immersible buoy having an inflatablebag surrounded by a perforated shell.

7. An immersible oil fence assembly according to claim 1 and furthercomprising an immersible terminal buoy having an inflatable air bag, acontact belt member extending from one end of said oil fence line, arope guide means secured to said oil fence assembly in the proximity ofsaid contact belt member, a rope means extending from a wall to whichsaid contact belt member is to engage said terminal buoy through saidrope guide means, a flexible air hose connecting said inflatable air bagof said terminal buoy to one of said immersible buoyancy generatingmeans of the oil fence assembly, and an air valve means controlling airflow through the last mentioned air hose for regulating the buoyancy ofsaid terminal buoy, whereby upon immersion of said terminal buoy, saidrope means acts on said rope guide means so as to force said contactbelt member to always engage said wall for terminating said oil fenceline at the wall.

8. An immersible oil fence assembly according to claim 7, wherein saidterminal buoy is an immersible buoy having an inflatable air bagsurrounded by a perforated shell.

9. An immersible oil fence assembly according to claim 1 and furthercomprising a central weight member located at the central portion of theoil fence line, a contractible hose means connecting said central weightmember to said tubular float means at about the center of said oil fenceline, said contractible hose means communicating with said tubular floatmeans, an additional air valve means connected to said blocked end ofsaid oil fence line in communication of said tubular float means,whereby upon opening one of the two air valve means connected to theopposite ends of the oil fence line, that half of the oil fenceline'lying between the valve thus opened and said central weight isimmersed.

10. An immersible oil fence assembly according to claim 9, wherein theopposite ends of the oil fence line are mechanically bonded together toform a closed loop.

11. An immersible oil fence assembly according to claim 5, wherein saidcontrollable weight member consists of a solid weight member and aninflatable hose section, which hose section is sealingly secured to saidsolid weight at one end thereof and communicates with said tubular floatmeans at the opposite end thereof, the inner volume of said hose sectionwhen inflated by filling air therein being large enough to generate sucha buoyancy which causes the solid weight member to leave the groundlevel under water.

12. An immersible oil fence assembly according to claim 1 and furthercomprising a solid weight member integrally secured to said blockingmeans and an inflatable hose section having one end thereofcommunicating with said tubular float means, said inflatable hosesection holding said solid weight member at the opposite end thereof soas to hang said weight member from said blocked end of said oil fenceline.

1. An immersible oil fence assembly, comprising a plurality of oil fenceunits having an elongated flexible belt member and a tubular float meanssecured to the belt member so as to extend along the longitudinal centerline of the belt member, a plurality of immersible buoyancy generatingmeans having an inflatable air container disposed therein, said oilfence units and said buoyancy generating means being alternatelyconnected while joining said tubular float means of adjacent ones ofsaid oil fence units to said air container of the buoyancy generatingmeans located therebetween, so as to form an oil fence line, anchorsstationed on the ground level, wire rope means connecting each of saidanchors to corresponding one of said immersible buoyancy generatingmeans, respectively, said wire rope means being long enough to cause thebuoyancy generating means to float on water surface, a blocking meansairtightly blocking said tubular float means at one end of said oilfence line, a flexible air hose connected to the opposite end of saidoil fence line, and an air valve means connected to said air hose andselectively feeding and releasing air into and out of said tubular floatmeans and said air container of the buoyancy generating means.
 2. Animmersible oil fence assembly according to claim 1, wherein each saidbuoyancy generating means is an immersible buoy having an inflatable airbag surrounded by a perforated shell.
 3. An immersible oil fenceassembly according to claim 1, wherein each said buoyancy generatingmeans is a second oil fence unit consisting of a second belt memberaligned with said belt member of said oil fence unit, an inflatablesecond tubular float means aligned with the tubular float means of saidoil fence unit and having a diameter larger than that of said tubularfloat means of the oil fence unit, and a metallic strap means integrallybonding said second tubular float means to said second belt member. 4.An immersible oil fence assembly according to claim 1 and furthercomprising a pilot float means anchored to ground level through a wirerope means so as to float on water surface substantially at a constantlocation, said air valve means being mounted on said pilot buoy.
 5. Animmersible oil fence assembly according to claim 1 and furthercomprising a controllable weight member secured to the wire rope meansconnecting the blocked side end buoyancy generating means to the anchorassociated with said end buoyancy generating means at an intermediateposition between said end buoy and said associated anchor, saidcontrollable weight member having an inflatable air chamber, and aflexible air hose connecting air container of said end buoyancygenerating means to said air chamber of said controllable weight member,the connecting position of said controllable weight member to said wirerope means being such that said controllable weight member is alwayskept below water level.
 6. An immersible oil fence assembly according toclaim 5, wherein said controllable weight member is an immersible buoyhaving an inflatable bag surrounded by a perforated shelL.
 7. Animmersible oil fence assembly according to claim 1 and furthercomprising an immersible terminal buoy having an inflatable air bag, acontact belt member extending from one end of said oil fence line, arope guide means secured to said oil fence assembly in the proximity ofsaid contact belt member, a rope means extending from a wall to whichsaid contact belt member is to engage said terminal buoy through saidrope guide means, a flexible air hose connecting said inflatable air bagof said terminal buoy to one of said immersible buoyancy generatingmeans of the oil fence assembly, and an air valve means controlling airflow through the last mentioned air hose for regulating the buoyancy ofsaid terminal buoy, whereby upon immersion of said terminal buoy, saidrope means acts on said rope guide means so as to force said contactbelt member to always engage said wall for terminating said oil fenceline at the wall.
 8. An immersible oil fence assembly according to claim7, wherein said terminal buoy is an immersible buoy having an inflatableair bag surrounded by a perforated shell.
 9. An immersible oil fenceassembly according to claim 1 and further comprising a central weightmember located at the central portion of the oil fence line, acontractible hose means connecting said central weight member to saidtubular float means at about the center of said oil fence line, saidcontractible hose means communicating with said tubular float means, anadditional air valve means connected to said blocked end of said oilfence line in communication of said tubular float means, whereby uponopening one of the two air valve means connected to the opposite ends ofthe oil fence line, that half of the oil fence line lying between thevalve thus opened and said central weight is immersed.
 10. An immersibleoil fence assembly according to claim 9, wherein the opposite ends ofthe oil fence line are mechanically bonded together to form a closedloop.
 11. An immersible oil fence assembly according to claim 5, whereinsaid controllable weight member consists of a solid weight member and aninflatable hose section, which hose section is sealingly secured to saidsolid weight at one end thereof and communicates with said tubular floatmeans at the opposite end thereof, the inner volume of said hose sectionwhen inflated by filling air therein being large enough to generate sucha buoyancy which causes the solid weight member to leave the groundlevel under water.
 12. An immersible oil fence assembly according toclaim 1 and further comprising a solid weight member integrally securedto said blocking means and an inflatable hose section having one endthereof communicating with said tubular float means, said inflatablehose section holding said solid weight member at the opposite endthereof so as to hang said weight member from said blocked end of saidoil fence line.